Volumetric properties of tripeptides with non-polar side-chains: Partial molar volumes at T = (288.15 to 313.15) K and partial molar expansions at T = 298.15 K of some peptides of sequence gly–X–gly in aqueous solution

Solution densities have been determined for aqueous solutions of the tripeptides of sequence glycyl–X–glycine, where X is one of the amino acids alanine, valine, leucine, isoleucine, phenylalanine, methionine, and proline, at T = (288.15, 303.15, and 313.15) K. These solution densities were used to calculate the partial molar volumes at infinite dilution, V2∘, for the tripeptides. The V2∘ results were combined with those determined in previous work for T = 298.15 K to obtain the partial molar isobaric expansions at infinite dilution, E2∘{E2∘=(∂V2∘/∂T)p}, for the tripeptides at T = 298.15 K. The contribution of amino acid side-chain hydration to the E2∘ results has been discussed.